Retinal detachment is a disorder of the eye in which the retina separates from its underlying layer of support tissue. Initial detachment may be localized, but without prompt treatment, the entire retina may detach, leading to vision loss and eventually blindness.
The retina is a thin layer of light sensitive tissue on the back wall of the eye. The optical system of the eye (cornea and lens) focuses light on the retina similar to the way light is focused on the film of a camera. The retinal tissue translates the focused image into neural impulses and sends them to the brain via the optic nerve. Occasionally, Posterior Vitreous Detachment (PVD), injury or trauma to the eye or head, or other conditions may cause a small tear in the retina. The tear allows vitreous fluid to seep through and collect under the retina, lifting the retina, and allowing it to peel away or otherwise separate from the underlying tissue.
There are several methods for treating a detached retina, which involve finding and closing any breaks that have formed in the retina. For example, pneumatic retinopexy is a procedure, which may be performed in a physician's office or operating room, e.g., under local anesthesia. A gas bubble is injected into the eye after which laser photocoagulation or cryopexy treatment may be applied to the retinal hole, break, or tear. The patient's head is then positioned so that the bubble rests against the retinal tear. Patients may keep their heads tilted or lie face down, e.g., for several days or other period of time, to keep the gas bubble in contact with the retinal tear. Surface tension of the gas/water interface may seal the tear in the retina, and allow the retinal pigment epithelium (RPE) to pump the subretinal space dry and draw the retina back into place.
Generally, pneumatic retinopexy involves the use of a one or three milliliter (1 or 3 ml) syringe typically filled with 0.3 to 0.6 ml of expansile gas and using a small gauge needle, e.g., 30 gauge or smaller. The syringe may be manually filled with gas transferred from a reusable pressurized gas canister containing one of a number of expansile gases, e.g., SF6, C3F8, or C2F6. The gas canister has a reusable pressure regulator, e.g., set to 10 psi, to reduce the pressure of the gas in the gas canister before being discharged into the syringe. A 0.22 micron or smaller filter is typically used to ensure the gas transferred to the syringe is free of contaminants.
With the syringe plunger fully depressed, a filter is connected to the distal end of the syringe, and the syringe-filter assembly is subsequently connected to the regulator attached to the gas canister. Typically, the syringe includes a male luer fitting and the filter includes male and female luer fittings on either end, with the female fitting connected to the syringe's male fitting, leaving a male fitting to the connect to the regulator. Typically, the regulator also includes a male luer fitting, and so a female-to-male luer adapter is generally used to make the connection between the filter and the regulator. Given the multiple connections typically involved, there is some risk of the pressurized gas escaping and/or air leaking into the system and into the syringe, thereby reducing the effectiveness of the gas delivered using the syringe.
Once the necessary connections are made, a valve of the gas canister is opened to release gas to the regulator and a valve on the regulator is opened to release regulated gas to the connected syringe-filter assembly, i.e., into the interior of the syringe. Generally, with the syringe plunger fully depressed, the regulated gas may be drawn into the syringe, e.g., based on the pressure of the regulated gas and/or manual retraction of the plunger. For example, the pressure of the gas may be sufficient to push the plunger back automatically during the filling process and fill the interior of the syringe with gas.
However, with many small diameter syringes, the regulated pressure (e.g., 10 psi) may not be enough pressure to push the plunger, e.g., due to the relatively high friction between the plunger and syringe wall and/or the small surface area of the piston contacted by the regulated gas, and so the clinician may need to pull on the plunger to complete the filling process. One of the risks of this action is that the clinician may pull too quickly, which may draw room air into the syringe, e.g., through the many connections, reducing the concentration of the gas (from 100%), thereby reducing the effectiveness of the gas tamponade provided when the gas is injected into a patient's eye.
To address this problem (since the pressure regulator is typically not adjustable and fixed at 10 psi), it has been suggested to fill a larger, e.g., 60 ml, syringe from the gas canister. Given the larger surface area of the plunger in such larger syringes, the regulated pressure may be sufficient to push the plunger and fill the larger syringe. Once filled, the larger syringe may then disconnected from the regulator (after closing the valve(s) of the gas canister and/or regulator) and connected to the smaller (e.g., 1 or 3 ml) syringe-filter assembly described above, e.g., using a female-to-female adaptor. The plunger of the larger syringe is then depressed to eject the gas therein and create sufficient pressure to push the plunger of the smaller syringe and fill the smaller syringe, thereby transferring the gas from the larger syringe to the smaller syringe for use during a procedure. Thus, this filling procedure may require multiple steps, which may increase the length of the time of the procedure and/or risk leakage of the pressurized gas and/or introduction of air into the syringe.
After filling the 1 or 3 ml syringe (whether from a larger syringe or directly from the gas canister and regulator), the filter is disconnected from the syringe and a needle is connected to the syringe, e.g., a 30 gauge or other relatively small gauge needle with a female luer fitting. The syringe is then ready to be used during a medical procedure, e.g., a pneumatic retinopexy procedure.
Upon completion of the procedure, single-use items, e.g., the syringe, needle, and filter, are disposed of, and reusable items, e.g., the gas canister and its pressure regulator, are closed and stored for future use. For example, the regulator is closed after filling the larger syringe or the smaller syringe (if filled directly from the gas canister), and the gas canister is closed to prevent gas leakage during storage and/or between procedures. Thus, one of the additional risks of conventional systems and methods is that the clinician or other user may forget to close the valve(s) of the regulator and/or gas canister or may not fully close the valve(s), thereby releasing pressurized gas from the gas cylinder. Such loss may increase the cost of future procedures since additional cylinders of gas will be needed, and/or may potentially release harmful greenhouse gases into the atmosphere. Further, if the gas cylinder is drained unexpectedly while in storage, the lack of pressurized gas may not be discovered until immediately before another procedure, which may disrupt patient flow and/or treatment while additional gas cylinders are obtained.
Accordingly, devices for loading syringes and/or performing retinal repair procedures would be useful.